This invention generally relates to adjustable connecting apparatus, and in particular to apparatus for fixedly adjusting the position of the bearing in a pivoted pad journal bearing.
Fluid film bearings are frequently required in rotating machines where speed and endurance requirements are beyond the capability of rolling contact bearings. Such machinery often requires bearing configurations which are highly stable and free from whip and whirl problems. Such bearing designs tend to be complicated and consequently expensive relative to other types of bearings.
One known type of fluid film bearing is a pivoted pad journal bearing, examples of which are shown in U.S. Pat. No. 3,572,856 of McHugh and in U.S. Pat. No. 3,497,276 of McGrew, Jr., et al. As discussed in the patent of McHugh, in order to achieve the requisite stability, it is essential to properly set the pivot circle clearance, i.e., the clearance between the pivoted bearing pad and the journal of the rotating shaft borne thereby. The amount of clearance even in rotating machinery of large dimensions must be kept on an order of a few mils. It is known to make such adjustment by means of threadably adjustable coupling arrangements. However, as noted by McHugh, precise adjustment is difficult due to the existence of a thread clearance between the threaded coupling members which permits backlash, i.e., relative lateral movement therebetween. A known approach to solve the backlash problem has been the use of spring members which act on the coupling members to press the threads together in a given axial direction.
Due to mechanical wear, etc., machines operating continuously often require routine maintenance adjustments of the pivot circle clearance. Ready access to the adjustment mechanism thus becomes very important in order to keep the time, and thus the expense, of routine maintenance to a minimum. One known technique for achieving easy accessibility has been to mount the bearing pads within a bearing housing or collar which is attached to and extends outwardly from a wall of the machine housing, or is otherwise supported in a location spaced therefrom. The adjustment mechanisms extend through the collar in a radial direction and have manually engageable parts located at the exterior of the collar and spaced from the machine housing.
While mounting the bearing assembly within a bore of the housing wall itself has advantages over the technique of mounting the bearing assembly within a collar separately attached to the machine, accessibility problems have detracted from the use of this mounting approach. The support to the bearing assembly provided by a bore contained within the wall of a machine housing is of equal or greater strength than that provided by an attached bearing assembly collar. Further, even when an attached collar is utilized, a bore must still be provided for passage of the shaft through the housing wall from the interior thereof so that it may be engaged by the bearing assembly exterior of the wall. Fabrication time is reduced by eliminating the need for attaching the bearing collar to the machine housing.